| Properly running in a new engine is one of the most important steps you can take to get the most life and power from your engine. Most new engines provide good instruction on how to run in your new engine. You should follow these Instructions and your engine should be place in a test mount for easy access.
However if your engine happens to come with no instructions or poor ones these tips should help. Most engines require about 30 to 40 minutes of run in time before they will run consistently.
First place the engine in a quality test stand for easy access. Open the carburetor to the full power setting and if your engine has a Low (idle) adjustment needle, turn it until its about 1/16 or so gap between the two needles in the center of the carb. Turn in the main needle until it seats then back it out 2 to 2.5 turns
You should be using no more than 10% nitro and you should add castor oil to the fuel 2.5 tablespoons to 4 to 5 oz of fuel to start with.
Start the engine and set the power to about ¼ to ½ throttle (enough power so that it doesn't sound like it wants to die) Begin to make the main needle richer until the engine sounds like it wants to die then lean it out a little. Allow the engine to run at this setting for about 5 to 10 minutes or until it uses the 4 to 5 oz of fuel. The Head of the engine should not get above 175 to 185 degrees F and the engine should be at a high idle speed, some where around 4 or 5 thousand RPM. Raytek makes great non contact thermal temperature reading equipment. Check Them Out!
This time only add about 1 to 1.5 tablespoons of castor oil to 5 oz of fuel. Start the engine up with the same setting, once it is running lean the main needle about a half turn or so and slowly rev the engine up until is running significantly faster than it was. Allow it run like this for about 1 minute then idle back down and make the main needle richer, as it was before. Let it run this way for a minute or two then repeat the process until it runs out of fuel.
Do the same as the second run but without any extra oil in your fuel. Once your down to about ½ tank run lean the engine as you did before but go just a little leaner and rev to full power for a short burst ( 30 sec or so). Rev the engine up quickly and adjust the idle needle so there is not much hesitation in the engine's rev up. As the tank nears empty rev to full power and then lean the engine until it reaches peak RPM then make it slightly richer and idle back to a high idle setting.
Let the engine run at idle for a bit then full power for a about a minute or so then back to idle do this for about 5 minutes and adjust settings if you feel they need it. At this point the engine should reach full power throttle up quickly and idle low. General running should be smooth and the engine should not die. If so it should be ready to mount to your plane. Allow another hour or so of flight time for the engine to fully break in.